[Supras] MHG's (now cam oiling)

[Hacker J]

I believe the general consensus is that the 86-88 square mounts are nearly unbreakable, whereas the 89+ mounts are softer but somewhat weaker. According to others, I have not tried this, the -88 mounts will support the weight of the entire front end when lifted by the engine alone, whereas the 89+ will tear out before the wheels lift off the ground.

The 98 mkiv mount (Bernie, I originally posted that info to this list although the credit for the find goes to Aaron at driftmotion.com) is alot tougher but be prepared for more vibration through the steering wheel.

It is certainly true that they are not defective though, as most seem to last 17+ years at stock HP.

I agree with Bernie's comments on the cam oiling. It is not a defect in the sense of causing catastrophic failure like a BHG, but the wear is high in the cam saddles. I have seen it on my own car and it has been treated nicely its whole life. The JZ engines definitely improved in the area of the top end lube design (center oil feed for example), along with bigger journals.

Jon
90T



----- Original Message ----



Content-Transfer-Encoding: 7bit
From: "Jeff Mohler" <speedtoys.racing at gmail.com>
Precedence: list
MIME-Version: 1.0
Cc: SPOOLED91T at aol.com, Supras at supras.com, Bigmacz28 at aol.com
To: berniek at technicaldevelop.com
References: <d58.2383bc9.3303aff1 at aol.com>
    <01ad01c74fd4$98a6fc90$0201a8c0 at ValuedVPRMatrix>
    <009401c74ff3$888b8280$0101a8c0 at Adminisrator>
    <a969fbd10702132058r89de977ie43351d8621282ed at mail.gmail.com>
    <010301c74fff$9eb70dc0$0101a8c0 at Adminisrator>
In-Reply-To: <010301c74fff$9eb70dc0$0101a8c0 at Adminisrator>
Date: Tue, 13 Feb 2007 22:31:07 -0800
Message-ID: <a969fbd10702132231g5281dbcdhd1c7522d27ace1a0 at mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Subject: Re: [Supras] MHG's (now cam oiling)
Message: 3


I dunno..I like to see clear evidence of failure across the board (like
BHGs) before I call something a design flaw.

Sorta like when you saw motor mounts as a huge flaw when you started on your
car..theres no issue, just YOU had bad ones, and after 20+ years, they had
the right to be bad.

Your low miles engine with severe erosion is not typical to the rest of us,
even with 100s of 1000s of miles.

On 2/13/07, berniek at technicaldevelop.com <berniek at technicaldevelop.com>
wrote:
>
>  Jeff:
>
>     My JDM did not have that many miles on it either.  The cylinders were
> not worn more than 1/2 thou or so, and the main and rod bearings were in
> like new condition.
>
>     However, the camshaft journal caps were worn, especially on the
> exhaust side, where the rearmost ones plastigaged at .006".  The problem is
> the lack of oil feed to the head, and the fact that all of the journals are
> cross-drilled.  As I'm sure you know, oil is fed into the hollow cams at
> only the front journal.  As a little wear occurs, there is less and less oil
> for the rear journals.  That is especially true at high speed because the
> oil tends to be thrown out of the journals increasing as the square of
> speed.  So less and less oil is available for the rearmost journals.
> Moreover, the oil passages in the block and head which feed the cams are
> small.
>
>     As my rebuild wears, I'll probably refinish the caps every 20K miles
> or so.  But the thought did occur to me to drill into the 7th exhaust
> journal support in the head, intersecting with another drilled passage on
> the exhaust side, and run an external oil line to feed at least the exhaust
> cam from both ends (with a groove machined in its rearmost journal).  But
> one problem with doing that is the reduction in head saddle journal support
> width.  It reduces down directly under the cam journals, so putting an oil
> feed hole in the rearmost one and grooving the cam journal itself for oil
> feed might be self-defeating.
>
>     Strange that the bottom end is built like the proverbial outhouse
> (with proper oil pan pickup provisions), but the top end oiling provisions
> are far from the best.
>
>             Bernie







 
____________________________________________________________________________________
Need Mail bonding?
Go to the Yahoo! Mail Q&A for great tips from Yahoo! Answers users.
http://answers.yahoo.com/dir/?link=list&sid=396546091